We will compare dexamethasone suppression iodocholesterol (NP-59) uptake and scanning by the adrenal cortex in another 30 patients with low renin essential hypertension. We will compare the uptake in patients with normal renin and high renin hypertension. We will similarly amplify our findings in non-hypertensive women on oral contraceptives. In dogs we will finish our evaluation of the effect of diuretics and low and high salt diet on these adrenal cortical functions. We will also study NP-59 transport and uptake mechanisms. In the adrenal medulla, we will amplify our findings in humans on the uptake of radioiodinated guanidine analogs in adrenal medullary hyperplasia, pheochromocytomas and neuroblastomas. We will radioiodinate and evaluate the uptake of alpha-methyl-paraiodobenzylguanidine in the adrenal medulla. The mechanism of the localization of these compounds in the adrenal medulla will be studied by autoradiography and subcellular fractionation.